Social anxiety disorder (SAD) is a pattern of pronounced and enduring fear and anxiety about being scrutinized in social interactional, observational, or performance situations (American Psychiatric Association, 2013). Negative social experiences (i.e., social traumas) have been implicated in etiological models of SAD (Kimbrel, 2008; Ollendick & Hirshfeld-Becker, 2002; Rapee & Spence, 2004). Research evidence links peer victimization with adolescent SAD symptoms and suggests the type of victimization may differentially influence symptom presentation (e.g., Storch, Brassard, & Masia-Warner, 2003; Storch & Masia-Warner, 2004). Preliminary evidence suggests that severity of reaction to social trauma may also influence the presentation of SAD symptoms (Levinson, Langer, & Rodebaugh, 2013; Rosen, Underwood, Gentsch, Rahdar, & Wharton, 2012). The current investigation utilized a retrospective design to examine how experiences of different types of social traumas (i.e., antagonistic vs. non-antagonistic), and severity of reaction to social traumas, relate to SAD symptoms in early adulthood. The influence of betrayal on severity of reaction to social traumas was explored, as well as the temporal relationship between the experience of social traumas and the onset of social anxiety symptoms. North American participants (n = 173; ages 18 to 25) completed an online battery of questionnaires measuring social anxiety symptoms, experiences of social traumas, and reactions to past social traumas. Regression and mediation analyses were used to characterize the relationships between social trauma frequency, reaction severity, and social anxiety symptoms. The relationships between frequency of both covert peer victimization and non-antagonistic social traumas and social anxiety symptoms appeared to be mediated by trauma-like responses. Betrayal did not appear to influence severity of social trauma response. The majority (62%) of participants experienced a social trauma following the onset of their symptoms. The results of the current investigation suggest that certain types of social traumas may play a more poignant role in the maintenance of social anxiety symptoms, largely through trauma-like reactions to such events. Understanding the nature of aversive reactions to socially traumatic events can inform cognitive behavioural treatment approaches and improve therapeutic efficacy.